‘Spineless': the plight of freshwater invertebrates a serious cause for concern

One-fifth of invertebrates around the world are threatened with extinction. Of these, freshwater invertebrate species face the highest risk of extinction.

A report into the status of the world’s invertebrate species, titled ‘Spineless’, was presented last month at the IUCN World Conservation Congress. Spineless was the work of the Zoological Society of London (ZSL) and the International Union for the Conservation of Nature (IUCN) and highlights the plight of the world’s many invertebrate animals. But why exactly are these figures so worrying? Why should we care about these spineless creatures?

The Tasmanian giant freshwater crayfish is the largest freshwater invertebrate in the world. This endangered crayfish lives in the freshwaters of Tasmania’s streams and rivers and faces threats from illegal fishing, land clearing and forestry. Photo: The Australian

Well, invertebrates make up a staggering 80% of all species in the world, play crucial roles in many ecosystems and provide enormous benefits to humans. For example, the common (but declining) bee contributes billions of dollars to the global economy each year through their role as pollinators and food producers.

Invertebrate species can be found all over the world and in many different and diverse ecosystems. But from a freshwater perspective this report is particularly alarming because the vast majority of the world’s estimated 126,000 freshwater species are invertebrates. What’s more is that the report assessed some 12,000 different invertebrate species around the world and found that invertebrates living in freshwater ecosystems are the most at risk of extinction. Terrestrial invertebrate species face the next highest risk, followed by marine invertebrates.

The report used global, regional and national level analyses and assessed the threats to 7,784 freshwater invertebrates, which is about 10% of all known freshwater invertebrate species. Examples of spineless freshwater animals include insects such as dragonflies, molluscs such as clams and mussels, and crustaceans such as crayfish and crabs.

Azure damselfly. Photo under Creative Commons Licence.

The report found that freshwater molluscs are among the most threatened group of animals on the planet – over half of all sea snails and over a third of all bivalves (clams, etc.) are threatened with extinction. About a third of all freshwater crabs and crayfish also face the risk of extinction and 15% of dragonflies and damselflies are at risk.

This is a serious cause of concern because of the crucial role freshwater invertebrates play in the functioning of ecosystems and the importance to people’s livelihoods. The benefits that freshwater invertebrates provide include water filtration and quality control, nutrient cycling, developing aquatic habitat structure, pest control, and as a food source for other animals. In addition, numerous crabs and crayfish act as keystone predator species in many ecosystems keeping other species numbers under control.

In terms of direct benefits to people, many freshwater invertebrates such as clams, mussels, sea snails, crabs and crayfish are of high commercial importance as food or ornaments for many people around the world. In addition to the valuable ecosystem services that these creatures provide, they also have value that it is less tangible, but by no means less significant. Many of our favourite lakes, rivers and streams would be very different places without the presence of these important but often under-appreciated animals.

One of the biggest threats to freshwater invertebrate species is water pollution caused by chemical from agricultural run-off, domestic sewage, and industrial waste as many species are incredibly sensitive to environmental change. The construction of dams, water extraction, and developments disrupting freshwater habitats, are also threatening the survival of freshwater invertebrates.

This worrying report demonstrates the urgent need to raise the conservation profile of invertebrate species, and in particular, freshwater invertebrates. The case for protecting these species needs to be made and coming up against more charismatic animals such as pandas and tigers no doubt makes the task all the more difficult in a resource constrained world. But, as outlined above, there are many reasons to protect these critters from extinction.

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